After reviewing several of the newer tools on this list last year I decided to go with JQuery. I wanted to upgrade a fairly large web app that I had used Prototype.js and Scriptaculus.js for client side work.
JQuery was easier for me to just start using than the others. I didn't need to learn anything and the docs and example code available are extensive and top notch, and there are very few questions I ran into that weren't already answered on Stackoverflow.
JQuery was easier for me to just start using than the others. I didn't need to learn anything and the docs and example code available are extensive and top notch, and there are very few questions I ran into that weren't already answered on Stackoverflow.